It is proposed to investigate biogenic amine metabolism in premature infants with recurrent apneic episodes, and in infants who have expired meeting the criteria of the Sudden Infant Death Syndrome. Brain material from 7 individuals aged 3 weeks to 43 years of age who expired suddenly of violent means and without antecedent illness have been assayed for noradrenalin, serotonin, catechol-O-methyl transferase, monoamine oxidase, and lactic dehydrogenase. These assays were performed in 19 discreet brain areas. When expressed as a ratio of catechol-O-methyl transferase or monoamine oxidase activity to lactic dehydrogenase activity, no significant differences were noted for the infants compared to the adults. Similar analyses performed on brain material from infants who have expired with SIDS is pending. Periodic samples of blood have been obtained from premature infants manifesting apnea. Plasma has been assayed for pyridoxal-5-phosphate and dopamine-beta-hydroxylase. Erythrocyte preparations were assayed for catechol-O-methyl transferase activity. Pyridoxal-5-phosphate levels appeared to reflect primarily the maternal nutritional status and the time the infant initiated feeding. In a majority of subjects, plasma dopamine-beta-hydroxylase activity increased progressively with age, being up to 10 fold greater at 22 days of age than at 8 hours.